1. Field of the Invention
The present invention relates to a broadcast receiver for receiving the broadcasting of a prescribed channel transmitted from a broadcasting station by a directivity switching antenna.
2. Description of the Related Art
In Japan, the airwave of a television broadcasting or the like is ordinarily transmitted from one base station. Accordingly, an antenna for receiving the broadcasting is fixed to a roof or a veranda of a residence toward the base station. The antenna is connected to a broadcast receiver so that the broadcasting transmitted from a plurality of broadcasting stations can be substantially entirely received. As compared therewith, overseas such as USA, airwaves are respectively individually transmitted from a plurality of broadcasting stations. Therefore, when the antenna is secured toward one direction, the broadcasting of the broadcasting station located in a direction to which the antenna is directed can be received, however, the broadcasting of the broadcasting station located in a direction to which the antenna is not directed cannot be received.
Thus, by considering the above-described circumstances, a broadcast receiver using an antenna capable of switching directivity (refer this antenna to as a directivity switching antenna, hereinafter.) has been proposed (see JP-A-2001-168627 (paragraphs 0019 to 0028, FIG. 2), JP-A-6-334931 (paragraphs 0041 to 0052, 0061, 0062, FIG. 7) and JP-A-11-298226 (paragraphs 0009 to 0015, FIG. 5, FIG. 6, FIG. 10)). The directivity switching antenna is composed of a plurality of antenna elements and phase devices respectively corresponding to the antenna elements. The phases of signals respectively received by the antenna elements are controlled by the phase devices and synthesized to electrically vary the directivity. For instance, in a smart antenna as one example of the directivity switching antenna, the directivity is switched to 16 directions in the periphery, which is specified by a standard. The broadcast receiver controls such a directivity switching antenna to switch the directive direction of the antenna to a prescribed direction so that the broadcast receiver receives the airwave of a prescribed channel transmitted from a prescribed broadcasting station. Thus, even when the directivity switching antenna is fixed to the roof of the residence, the user can receive substantially all of the broadcasting transmitted from a plurality of dotted broadcasting stations.
In the above-described broadcast receiver, when a desired channel is set as a receiving channel, the user operates an operating unit such as a remote controller or a switch to select one desired channel, and then operates the operating unit to switch the directive direction of the directivity switching antenna. Specifically, a control unit of the broadcast receiver switches the directive direction of the directivity switching antenna in accordance with an operating instruction of the user. At this time, the control unit processes the airwave received by the directivity switching antenna to display an image on, for instance, a television receiver (refer it to as a TV set, hereinafter.). Further, the control unit may sometimes display a character showing the current directive direction of the directivity switching antenna on the TV set (see JP-A-6-334931). While the user watches the TV set, the user operates the operating unit so as to display the best image and switches the directive direction of the directivity switching antenna. Then, when the directive direction of the directivity switching antenna in which the best image is displayed can be specified, the user performs a prescribed operation by the operating unit to set the receiving channel and the specified directive direction of the directivity switching antenna to the broadcast receiver. Thus, the control unit stores channel information showing the selected channel and direction information showing the directive direction of the directivity switching antenna at this time in a memory. When the receiving channel is set as described above, then, if the user operates the operating unit to select the set channel again, the control unit can read the direction information of the directivity switching antenna corresponding to the channel from the memory and switch the directivity of the directivity switching antenna to a direction shown by the direction information. Therefore, the broadcasting of the selected channel can be immediately received by the directivity switching antenna and the best image of the broadcasting is reproduced (displayed) on the TV set so that the user can immediately look at and listen to the TV set.
Further, there is a broadcast receiver that automatically determines the directive direction of a directivity switching antenna so that the level of the received electric power of a prescribed channel becomes maximum (see JP-A-11-298226). In this broadcast receiver, when a user selects a desired channel, a control unit controls the directivity of the directivity switching antenna to scan in an omni-direction, searches the direction of the maximum level of the received electric power and holds the directivity of the directivity switching antenna in that direction. Therefore, even when the user does not operate an operating unit to switch the directive direction of the directivity switching antenna, the broadcasting of the selected channel is received by the directivity switching antenna and the best image of the broadcasting is reproduced on a TV set so that the user can look at and listen to the TV set.
Some broadcasting stations broadcast only for a limited time, for instance, the broadcasting is performed during the daytime, however, the broadcasting is not performed during the night, among a plurality of broadcasting stations. When a channel that meets the broadcasting of the broadcasting station is set as a receiving channel in a usual broadcast receiver, if the channel is set to a time during which the broadcasting is carried out, a user can switch the directive direction of a directivity switching antenna to specify the directive direction in which the broadcasting can be most preferably received. However, when the channel is set to a time during which the broadcasting is not carried out, even if the user switches the directive direction of the directivity switching antenna, the user cannot receive the broadcasting itself. Thus, the directive direction in which the broadcasting can be most preferably received cannot be specified. Therefore, when the user tries to set the channel to the time during which the broadcasting is not carried out from a reason why the time during which the broadcasting is carried out is unclear, the user needs to recognize that the direction in which the broadcasting can be most preferably received cannot be specified, then, to select a suitable directive direction and to store channel information and direction information showing the selected directive direction in a memory. Thus, it takes undesirably much time to set the channel. Further, when the user suitably sets the channel as described above, the user subsequently selects the channel. At this time, even when a control unit reads the direction information corresponding to the channel from the memory and switches the directivity of the directivity switching antenna to the direction shown by the direction information, the broadcasting of the channel cannot be most preferably received. Accordingly, when the user tries to look at and listen to the broadcasting of the channel in a most preferable state, the control unit is restricted by the direction information stored in the memory. After the control unit firstly switches the directive direction of the directivity switching antenna to the direction shown by the direction information, the user undesirably needs to recognize that the switched direction is not a direction in which the broadcasting can be most preferably received. Further, while the user switches the directive direction of the directivity switching antenna, the user needs to search the direction for most preferably receive the broadcasting. Thus, it takes inconveniently much time to look at and listen to the broadcasting in the most preferable way.
On the other hand, the influence of an interfering radio wave flying about in the periphery is different owing to a receiving place, for instance, the influence of the interfering radio wave is weak during the daytime, but strong during the night depending on time. Accordingly, the directive direction of the directivity switching antenna in which the broadcasting of the prescribed channel can be most preferably received may be different depending on time. In such a receiving place, when the channel is set as the receiving channel in the usual broadcast receiver, the user subsequently selects the channel. At this time, even when the control unit reads the direction information corresponding to the channel from the memory to switch the directivity of the directivity switching antenna to the direction shown by the direction information, the broadcasting of the channel can be most preferably received for a certain time, however, the broadcasting of the channel cannot be most preferably received for another time. Accordingly, when the user tries to look at and listen to the broadcasting of the channel in a most preferable state for the different time, the control unit is restricted by the direction information of the memory as described above and firstly switches the directive direction of the directivity switching antenna. Then, the user needs to switch the directive direction and search the direction for most preferably receiving the broadcasting. Thus, it takes undesirably much time.
The present invention overcomes the above-described problems and it is an object of the present invention to provide a broadcast receiver that can reduce a time necessary for setting a channel and a time necessary until the broadcasting of the set channel can be looked at and listen to in a most preferable state.